Wednesday, November 30, 2011
Snakes and other venemous creatures got their poison by consuming these plants. And stinging insects got their little doses of poison by feeding off dead snakes.
Isn't that a great narrative? It explains everything, in a nice logical progression. OK, it presupposes what we would call a "supernatural" force as the ultimate origin of poison, but other than that, it's an entirely "scientific" account. In accordance with Occam's Razor, it proposes a single unified process underlying diverse phenomena.
It is, in other words, a perfect scientific theory. It's completely wrong, on every point, but we only know that because we now understand atoms, molecules, chemistry and biochemistry, which the Greeks had no way of knowing. At the time, the Hades theory was surely the best possible theory about where poison came from.
The moral of this story is, beware nice theories based on incomplete data.
Reference: Greek Fire, Poison Arrows and Scorpion Bombs, which I'm currently reading, all about chemical and biological weapons.
Tuesday, November 29, 2011
a new American Journal of Psychiatry paper that could prove controversial.
CBT is widely perceived as having a better evidence base than other therapies. The "creation myth" of CBT (at least as I was taught it) is that it was invented by a psychoanalyst who got annoyed at the unscientific nature of psychodynamic i.e. Freudian-influenced therapy. CBT has always looked on clinical trials more favorably than the dynamic school.
However, the authors of this meta-analysis found that while there are certainly lots of published CBT trials for depression, they're actually no better quality than the psychodynamic trials.
"Surprisingly" (their word), they found no difference between the CBT for depression trials, and the psychodynamic trials, on a rating score of trial methodology.
Trials got better over time, but the two groups improved equally (see above). The mean score was 25.5 for CBT and 25.1 for dynamic, on a scale that goes from 0 to 48. Anything over 24 points is deemed acceptable but this is clearly an arbitrary cut-off.
The RCTP-QRS scale is relatively new and it was developed by the people who wrote this paper (albeit with the input of other experts.) There's 24 items and each gets a score from 0 (bad) to 2 (good). Items are things like "Adaquate sample size", "Patients randomly assigned to group", etc.
Worryingly, better CBT trials tended to find smaller benefits of CBT over the comparison treatment. The overall results showed that while CBT was clearly better than doing nothing, it was pretty much the same as antidepressants, and other psychotherapies, in adults with depression:
The article follows one from the same group, Gerber et al, who reviewed the evidence for psychodynamic therapy in more detail. And last year, another team reported evidence of publication bias in psychotherapy trials. In this study, the authors report possible publication bias, but they don't go into detail.
Overall this is interesting stuff, and a reminder that while CBT has the most evidence of any psychotherapy, this is not the same thing as saying that it has the best evidence...
Nathan C. Thoma et al (2011). A Quality-Based Review of Randomized Controlled Trials of Cognitive-Behavioral Therapy for Depression: An Assessment and Metaregression American Journal of Psychiatry
Monday, November 28, 2011
“Parents have been begging us for help. We now have something that we really feel can assist their kids,” said Paul Casciano, the school superintendent. “We have students who are substance abusers. They are already here. And we need to help them.”
After news of deaths from heroin overdoses on Long Island made the news, came the realization that something had to be done to stem the tide of addiction. At William Floyd High School, 38 students had drug hearings and were subsequently suspended from school.
“We are bringing the services to them so that they have instant access to it. And it doesn’t have to build to a crisis,” said Caroline Sullivan of Daytop Adolescent Outreach.
Daytop Adolescent Outreach was chosen to run the program inside William Floyd High School. The program will not cost the school district a penny. The program is confidential and anonymous and is open only to students enrolled in the school district.
Drug treatment advocates are applauding the news of the high school’s drug treatment center.
“There’s a huge increase in heroin use among kids. We are watching more than 350 kids die a year due to overdoses – on Long Island, in Nassau (County) and Suffolk (County),” said Dr. Jeffrey Reynolds, an addiction specialist.
It is the hope that the drug treatment center at William Floyd High School will serve as a model for other drug treatment centers and that other high schools across Long Island will start similar programs in their schools.
Saturday, November 26, 2011
But even more importantly, it refers to a certain blog in the process:
The Student’s t-test merely quantifies the ‘Lack of support’ for no effect. It is left to the user of the test to decide how convincing this lack might be. A further difficulty is evident in the repeated samples we show in Figure 2: one of those samples was quite improbable because the P-value was 0.03, which suggests a substantial lack of support, but that’s chance for you! A parody of this effect of multiple sampling, taken to extremes, can be found at http://neuroskeptic.blogspot.com/2009/09/fmri-gets-slap-in-face-with-dead-fish.htmlThis makes it the second academic paper to refer to this blog as far. Although I feel rather bad about this one, since the citation ought to have been to the original dead salmon brain scanning study by Craig Bennett. I just wrote about it.
Actually, though, this editorial was published in five separate journals: The Journal of Physiology, Experimental Physiology, the British Journal of Pharmacology, Advances in Physiology Education, Microcirculation, and Clinical and Experimental Pharmacology and Physiology. Phew.
In fact, you could say that this makes not two but six citations for Neuroskeptic now. Yes. Let's go with that.
Anyway, after discussing the history of the ubiquitous Student's t-test - which was invented in a brewery - it reminds us that the p value you get from such a t-test doesn't tell you how likely it is that your results are "real".
Rather, it tells you how often you'd get the result you did, if there was no effect and it was just random chance. That's a big difference. A p value of 0.01 doesn't mean your results are 99% likely to be real. It means that there's a 1% chance that you'd get them, by chance. But if you did say 100 experiments, or more likely, 100 statistical tests on the same data, then you'd expect to get at least one result with a p value of 0.01 purely by chance.
In that case it would be silly to think that the finding was only 1% likely to be a fluke. Of course it could be true. But we'd have no particular reason to think so until we get some more data.
This is what the dead salmon study was all about. This multiple comparisons issue is very old, but very important. Arguably the biggest problem in science today is that we're doing too many comparisons and only reporting the significant ones.
Drummond GB, & Tom BD (2011). Statistics, probability, significance, likelihood: words mean what we define them to mean. British journal of pharmacology, 164 (6), 1573-6 PMID: 22022804
Friday, November 25, 2011
“A dangerous idea!” That was the response after a presentation I gave to a small group of academic leaders with an interest in psychopharmacology [over 15 years ago].
What evoked such a response? The acknowledgment that most currently available antidepressants specifically treat only one out of four patients with major depression based on the bulk of clinical trials data.
There was no argument about the accuracy of this statement, but...some claim it is “dangerous” to admit that the specific response rate to most antidepressants is 20%–30% because such an acknowledgment might undermine the value of antidepressant treatment.By the "specific" response rate Preskorn means the number of depressed people who'll get better on antidepressants and who wouldn't have done so well on placebo. This rate is fairly low because, while most people get better on antidepressants, most of those improve on placebo as well.
Preskorn rejects the view that it's dangerous to acknowledge this:
...there are several problems with this reaction. First, it is hard to deny reality. The “placebo” response rate in antidepressant trials is arguably the most reproducible finding in psychiatry. Moreover, if available antidepressants were magic bullets, then polypharmacy would not be so common. Second, this reaction ignores the fact that antidepressants are tremendously valuable to the patients who specifically benefit from them...
Every treatment in every area of medicine has limitations. Acknowledging that fact should galvanize us to action. Denial on the other hand perpetuates the status quo.Unfortunately, we're not told who these academic leaders were. I wonder if they included amongst their ranks some of the "key opinion leaders" in the field whose leadership proved rather less than ideal. The column is actually adapted from a 1996 article by Preskorn.
Preskorn is right, of course, that denying the fact that antidepressants are only substantially better than placebo in a fraction of people who get diagnosed with "depression" is wrong, and also misses the point: because hundreds of millions of Americans have diagnosable depression (due to the loose definition of "depression"), even if they only helped 1% of them, they'd still help over a million people.
But he doesn't mention that this approach was ultimately self-defeating. As a result of the failure to acknowledge that antidepressants are only helpful in some cases of depression (namely "severe" depression), these drugs became very widely used and - oh dear - people started saying that the drugs are being overused, and don't work in most people who take them.
Whoever could have seen that coming.
This has "devalued" antidepressants - and psychiatry itself - more than anything else has.
Preskorn SH (2011). What Do the Terms "Drug-Specific Response/Remission Rate" and "Placebo" Really Mean? Journal of psychiatric practice, 17 (6), 420-424 PMID: 22108399
Wednesday, November 23, 2011
I've done so in previous posts e.g. this one or this one.
Which is why a new paper is important. The authors, a large Turkish-American collaboration, found that mutations in a gene, WDR62, are associated with severe brain malformations in 9 patients. But what's interesting is that it doesn't cause any particular malformation.
If you have two faulty copies of this gene, your brain won't be normal, but what goes wrong varies widely amongst different people. Although the 9 cases had some features in common, such as microcephaly (small head and brain), in other respects they differed greatly.
As the authors put it, mutations in WDR62 cause
a wide spectrum of severe cerebral cortical malformations including microcephaly, pachygyria with cortical thickening as well as hypoplasia of the corpus callosum. Some patients... had evidence of additional abnormalities including lissencephaly, schizencephaly, polymicrogyria and, in one instance, cerebellar hypoplasia, all traits traditionally regarded as distinct entities.These are distinct entities, in the sense that you can have any one of them, without having the others. And they are different brain changes. What the authors mean is that everyone assumed that, because they're different, they must have different genetic causes. They've just shown that this is wrong.
So what is WDR62 "for"? Experiments in mice showed it to be involved in the migration of new neurons from their origin to their final location in the brain. So it's "for" correct neuronal placement, although how it works remains unclear.
WDR62 ought to remind us that there's a long and winding road from gene to phenotype, and that the same gene can, when mutated, cause very different symptoms. This is especially interesting in the light of recent evidence showing that the same mutations can cause a range of behavioural disorders from autism to ADHD to schizophrenia.
Bilgüvar K, et al (2010). Whole-exome sequencing identifies recessive WDR62 mutations in severe brain malformations. Nature, 467 (7312), 207-10 PMID: 20729831
Tuesday, November 22, 2011
Monday, November 21, 2011
A new paper makes the startling claim that Eva Peron may have received a prefrontal lobotomy in the months before her death. The lobotomy is best known as a treatment for mental disorders such as schizophrenia, but according to Nijensohn et al, Peron was given the operation as a kind of pain relief.
The claim was first made in 2005 by Dr George Udvarhelyi, who worked as a neurosurgeon in Argentina before moving to John Hopkins in Baltimore. After his retirement, Udvarhelyi told the Baltimore Sun that he'd performed the operation.
The authors of this paper checked out the claims against his unpublished memoirs. It turns out that they've just written Udvarhelyi's biography, and managed to slip in a plug for their book. Indeed, this paper could be seen as a plug. But anyway.
The early 1950s were the golden age of lobotomy and it does seem plausible that if she had one, it would have been kept secret. But it seems that the only direct evidence is Udvarhelyi's testimony. The authors point to various facts that could be seen as consistent with it, like this memoir by a close friend:
“The illness continued to advance. I visited her one afternoon andwas shown a notebook belonging to her brother Juancito. There was a drawing of Evita with her head criss-crossed by scissors. The sinister image suggested that she was either crazy or brain damaged. I found her very thin, quiet, and deeply introverted”But to be honest this is pretty weak. The authors also admit that in interviews with scholarly experts on Peron's illness, they were all surprised by the idea.
They then point to postmortem X-rays of Peron's skull which were made public in 1955 to prove that her corpse hadn't been burned (long story). These, they suggest, show evidence of the kind of burr holes that were used to insert the lobotomy tools -
Hmm. Not sure what to make of those. Ultimately though, the authors admit that the only way to know for sure would be to exhume Evita and study her skull, but this is unlikely to happen any time soon.
Nijensohn DE, Savastano LE, Kaplan AD, & Laws ER Jr (2011). New Evidence of Prefrontal Lobotomy in the Last Months of the Illness of Eva Perón. World neurosurgery PMID: 22079825
A lot of different factors cause drug abuse to rise and fall but if young people get the message that drugs are dangerous, they are less likely to use them. That is why an effort needs to be made to get young people to see the dangers of drug abuse and addiction. Parents, teachers, and doctors all need to work together to help prevent drug abuse and addiction by teaching young people the possible consequences.
Effects of Drug Abuse and Addiction
Drugs contain chemicals that affect the brain's ability to communicate with the rest of the body and to process data that comes into the brain. Drugs do this in a two different ways: by mimicking the chemicals the brain creates naturally and by causing excess production of the reward chemicals in the brain.
Marijuana and heroin are drugs that are made up of chemicals that are a lot like the neurotransmitters in the brain that send messages to the body.When you use these drugs, the chemicals they contain trick the nerve cells and receptors in the brain into releasing excess brain chemicals, which results in a unusual message being sent or the chemicals can prevent any messages from being sent at all. Cocaine and methamphetamine also affect the amount of neurotransmitter that is released and that causes the neurons to fire without stopping.
Drugs of all kinds have some effect on the brain's so-called reward system, which means they increase the amount of dopamine that is released. Dopamine is normally released naturally and makes you feel good. Too much dopamine production causes unusual thoughts and behavior as people feel euphoric. People then come to rely on the drugs to get those feelings of euphoria, which is what causes drug abuse and addiction.
The brain cannot produce the normal amount of dopamine when you are using drugs so without the drugs, you don't feel those good feelings like you normally would. People who abuse drugs keep taking more and more to try to feel good. This explains drug abuse and addiction.
When people suffer from drug abuse and addiction for a long time, their entire brain is affected. Neurotransmitters like glutamate, which is part of the reward system and helps you learn, can be altered and weakened when there is drug abuse. The brain then cannot function and the person can be cognitively impaired.
Drug abuse and addiction cause conditioned learning, which means an addict will crave the drugs when he is in a situation that is associated with drug use. When you look at the brain of someone who has abused drugs, you will see that his brain doesn't function well in areas that help him make good judgments, good decisions, learn things, and remember things. He also has trouble controlling his behavior. All these result in even worse drug abuse and addiction over time if nothing is done to stop it.
Saturday, November 19, 2011
In the near future, we might be able to routinely sequence the genome of any unborn child shortly after conceptionBut I didn't realize that this may be really very near indeed. Two recent reports have shown that it's possible to sequence fetal DNA from a maternal blood sample. In one case it was used to diagnose a 35 week fetus with a genetic deletion on chromosome 12 seemingly associated with autism, developmental delay and shortness.
de novo mutations that account for much disease, as I discussed in the last post.
This is big. Currently, the main way to get fetal DNA is through amniocentesis, i.e. inserting a needle into the womb. It's a substantial and not entirely safe medical procedure. A blood sample would be an order of magnitude cheaper and safer, but most of all it would be something you could do at home.
No longer would you need to go to a hospital and discuss everything with a doctor. You could take some blood, send it off anonymously to a sequencing company, and get the results in an email. It would take it out of the hands of professionals and open up a space for individual choice.
The cost of whole-genome sequencing has been falling exponentially and many think it will fall below the $1000 mark within a few years. Combine that with fetal DNA testing and we might see moderately well-off parents able to sequence fetal DNA within the next decade.
When this happens I think the personal genomics industry will suddenly become extremely "hot". At the moment you can sequence your own DNA for a few thousand $ if you want. The results may be interesting but they're of little obvious use. Whatever your genes are, you're stuck with them.
But as soon as we're talking about potential human genomes, it'll kick things up a notch. Media interest and political controversy is sure to follow. Personally I think it'll the debate will begin in earnest when we start seeing selective abortions on the basis of genes for "normal" variants rather than "disease" genes.
It's one thing to not want a child with blindness, or a high risk of leukaemia. But as a society I don't think we're ready for not wanting a child because they're predicted to be a B student rather than an A student, or brunette rather than blonde. At some point soon, though, we'll have to decide what we think about that.
Peters D, Chu T, Yatsenko SA, Hendrix N, Hogge WA, Surti U, Bunce K, Dunkel M, Shaw P & Rajkovic A (2011). Noninvasive prenatal diagnosis of a fetal microdeletion syndrome. The New England journal of medicine, 365 (19), 1847-8 PMID: 22070496
Srebniak M, Boter M, Oudesluijs G, Joosten M, Govaerts L, Van Opstal D, & Galjaard RJ (2011). Application of SNP array for rapid prenatal diagnosis: implementation, genetic counselling and diagnostic flow. European journal of human genetics : EJHG, 19 (12), 1230-7 PMID: 21694736
Friday, November 18, 2011
A startling new paper from Tehran claims Antidepressant effects of magnetic resonance imaging-based stimulation on major depressive disorder.
Yes, this study says that having an MRI scan has a powerful antidepressant effect.
They took 51 depressed patients, and gave them all either an MRI scan or a placebo sham scan. The sham was a "scan" in a decommissioned scanner. The magnet was off but they played recorded scannerish sounds to make it believable. Patients were blinded to group.
They found that people in the scanner group improved much more than those in the sham group over two weeks. Actually there were two different kinds of scans, T1 structural MRI and EPI functional MRI, but they were the same:
functional MRI, which is that it's a method of recording brain activity. If it's also stimulating the brain in some way at the same time, then it would make it hard to interpret those activations. In particular it would cast all the studies using fMRI in depression into doubt.
So is it true? I can't see any obvious flaws in the design. Assuming that the authors are right when they say that "patients could not distinguish the difference between the actual and sham MRI scan", i.e. assuming that the blind was truly blind, then the methodology was sound.
But let's look at the statistics. The paper is full of very impressive p values less than 0.001 but those turn out to all be referring to the changes within each group, and those changes are fairly meaningless. What matters is the differences in the groups and
Changes in BDI scores (between baseline and day 14) were significantly different among the three studied groups (F=5.48, p=0.007 overall) using ANOVA, and between the DWI group vs. Sham and T1 vs. Sham (p<0.05) using post hoc tests. Changes in HAMD24 scores (between baseline and day 14) were also compared among the 3 groups using ANOVA but the level of significance was slightly above the significance threshold (F=2.89, p=0.06).Which is rather less convincing. There was a close-to-significant group difference in the HAMD24, and a significant but only just effect on the BDI. Remember that there were only 17 people in each group.
I'm inclined to think that this is one of the 5% of experiments which will produce a nominally significant result even assuming everything goes to plan and there are no confounds. My suspicion is that everyone in the trial got better (they were all on antidepressants, plus there's the placebo effect and the effect of time) - except a small number of people who didn't improve. And by chance they were all in the sham group.
The reason I'm skeptical is that I just can't see a plausible mechanism. The authors suggest that MRI scans might stimulate the brain in a similar way to TMS and that this could have antidepressant effects.
But there's a lot of problems with this: 1) the evidence is questionable whether TMS even works for depression 2) the magnetic stimulation of the brain generated during MRI is much weaker than in the case of TMS and 3) if MRI really stimulated the brain like TMS, then, like TMS, it would have a risk of triggering seizures in people with epilepsy. But it doesn't.
Vaziri-Bozorg SM, et al (2011). Antidepressant effects of magnetic resonance imaging-based stimulation on major depressive disorder: a double-blind randomized clinical trial. Brain imaging and behavior PMID: 22069111
Thursday, November 17, 2011
Peer led drug rehabilitation center in Delhi " The New Beginning of New Life" members interacting with young members of Radio club
|Mr.Ganesh Thapliyal and Mr.Heera Singh Dhami from a peer led drug rehabilitation center the Beginning of a New Life|
|Pehachaan Radio club Balbhawan Mandi : An initiative of Nada India and Balbhawan|
Tuesday, November 15, 2011
Can it really be true that a quarter of Brits are bullied or beaten up at home or are mentally ill, or is this simply a case of social campaigners exaggerating how bad life is in order that they can continue to make headlines, make an impact, and get funding? I reckon it's the latter. Next time you see the "one in four" figure, be very sceptical – it's probably Dickensian-style doom-mongering disguised as social research, where the aim is to convince us, against the evidence of our own eyes and ears, that loads of the people we encounter everyday are basket cases in need of rescue.I say "argues against", but he doesn't actually provide any arguments. He just links to the claims and says they're silly.
As Neuroskeptic readers know, I am myself skeptical of the idea that one in four people are mentally ill, but I'm skeptical of it because I've looked at the evidence and it doesn't support that figure. Actually, if you take the available evidence at face value, it says that the true figure for the lifetime prevalence is much higher than one in four. I don't think those figures are very useful however because of various methodological issues.
So in my view we just don't know how many people are mentally ill, largely because we don't have any clear definition of what "mentally ill" means. But that doesn't mean we can just assume that it can't possibly be one in four just because "our own eyes and ears" tell us that most people are not "basket cases".
Much mental illness goes undiagnosed and unnoticed, and I'd imagine also that Brendan O'Neill and the kind of people who read him don't tend to "encounter everyday" people from groups such as the unemployed, the elderly and so forth, in whom the rates are higher.
But even beyond that, it's a silly argument because of selection bias. If you as a healthy person encounter someone everyday, chances are they're not severely ill - mentally or physically - because if they were, they'd be less likely to be around in places for you to encounter. Unless you're a doctor or whatever, you live your life in the world of healthy people.
It's like saying that you don't believe children or the elderly exist, because in your life as a working age adult, you never meet any of them.
Monday, November 14, 2011
On the one hand you have Susan Greenfield and her games-hurt-the-brain theory. But she's not representative of neuroscientists as a whole: games have also helped neuroscience, for example, in this study of the neural correlates of "flow" experiences.
Now neuroscientists have another reason to be thankful for games, according to a new paper. It turns out that modern 3D graphics cards - which mostly exist in order to render videogame visuals - can be used to do fMRI data analysis.
According to Sweden's Eklund et al, a graphics card can perform intensive fMRI analysis hundreds of times faster than a regular processor of the equivalent speed, because graphics processors make use of parallel computing optimized for 3D images and that's ultimately what all brain scans are.
They developed a way to run non-parametric statistical analyses of brain imaging data. Proponents say that non-parametric stats have many advantages over conventional parametric ones - and they're certainly becoming increasingly popular. But they involve doing far more calculations. Thousands of times more, in some cases.
NVidia GTX 480s, and making use of NVidia's graphics programming language, they were able to cut the time to analyse one person's brain with 100,000 permutations, from 24 hrs to just 9 minutes. The whole setup cost $4000, so it's not cheap, but they say it's "a fraction of the price for a PC cluster with equivalent computational performance" i.e. one relying on lots of general purpose processors, rather than graphics cards. Even on GTX480 did the job very well.
Best of all, this gives neuroscientists an excuse to spend their grant money on awesome gaming rigs. Why do I want the latest GForce on my work computer? To do non-parametric data analysis, obviously. Sure, it would also allow me to run Modern Warfare 3 at the highest settings... but that's not why I want it.
Eklund A, Andersson M, Knutsson H (2011). Fast random permutation tests enable objective evaluation of methods for single-subject FMRI analysis. International journal of biomedical imaging, 2011 PMID: 22046176
Sunday, November 13, 2011
The excessive intake of drugs or alcohol, so much so that a person is dependant on them and they become food and water for him is called "substance abuse." Currently, marijuana, ecstasy, and cocaine are some of the most widely used drugs in the world. This can have disastrous effects on the person's health. Substance abuse has also led to subsequent deaths for not having been treated on time.
Alcohol addiction also plays a big part in substance abuse. Initially, people just want to experiment and try out "something different." But as time passes, they get addicted even before they know it. It becomes exceedingly difficult for an alcohol addict to control his cravings at a later stage. Even if he wants to quit he just can't bring himself to do it.
If a loved one is facing victim to this addiction, then don't delay in admitting him to a rehab for substance abuse treatment. Once the source of the problem is tackled, the recovery is usually fast. A combination of drugs and meditation is used to treat the patient. Meditation is mainly done to soothe and calm the agitated and tensed mind of the person. This method is also known as the "Holistic Method of Healing."
However, you may have to be a little enduring because if the addiction is severe, the recovery may take longer than usual. Addiction has a deep psychological effect also so it is imperative that all the issues that are troubling the person should be tackled. This is done to prevent the relapses of addiction when the person is out of the rehab.
Saturday, November 12, 2011
Courchesne et al counted the number of cells in the prefrontal cortex of 7 boys with autism and 6 non-autistic control boys, aged 2-16 years old. The analysis was performed by a neuropathologist who was blind to the theory behind the study and to which brains were from which group. That's good.
They found that the total brain weight of the brain was increased in autistic boys, by about 17% on average. But the number of neurons in the prefrontal cortex was increased by an even higher margin - about 60%. The difference was specific to neurons - glial cell counts were normal. Of the 7 autistic boys, 4 also had intellectual disability - an IQ less than 70. However, the 3 without showed broadly similar results.
dysplasia in one case and abnormal cell orientation in another. And no fewer than 4 had flocculonodular lobe dysplasia in the cerebellum.
None of the nonautistic brains had any abnormalities reported but they don't seem to have looked very closely in the controls because that was based on "coroner's report only", rather than a detailed neuropathological exam...
It's a nice piece of work, but very small. These postmortem neuropathology studies always are because postmortem brain samples are in short supply, especially for disorders like autism.
In fact, it's so small, that doing statistics on these data is not really meaningful. The authors do some stats and get some impressive p values but we should take those with a pinch of salt and just look at the individual data (see the scatterplots above).
Now, prefrontal cortical neurons are generated while you're still in the womb. New ones can't be created after you're born - numbers can only decrease. So the increased neuron count in autism must have a very early origin, either genetic or caused by pre-natal environmental factors. Unless the timeline for cell genesis is totally different in autism.
Still, it casts doubt on the idea that, in the brain, bigger is always "better". Assuming that we consider autism to be "bad" - which I'm not saying is necessarily right, but it's fair to say most people do assume that - then the common practice of equating volume increases with all kinds of good things seems rather silly.
Courchesne E, Mouton PR, Calhoun ME, Semendeferi K, Ahrens-Barbeau C, Hallet MJ, Barnes CC, & Pierce K (2011). Neuron number and size in prefrontal cortex of children with autism. JAMA : the journal of the American Medical Association, 306 (18), 2001-10 PMID: 22068992
Thursday, November 10, 2011
A paper just out reveals that the snappily-named GSK372475 doesn't work and has lots of side effects. It's a report of two clinicals trials in which Glaxo's contender was pitched against placebo and against older antidepressants in the treatment of depression.
GSK372475 failed to improve depression any better than placebo, even though the trials were large (393 and 504 patients respectively) and twice as long as most antidepressant trials (10 weeks whereas 4 or 6 is more usual)which ought to have given it plenty of room to shine.
The comparison drugs, the widely used venlafaxine and paroxetine, did work. A bit.
Melancholia Subscale" as an outcome measure, which Neuroskeptic readers may remember as I've praised it before. Venlafaxine worked on that, GSK's new pill didn't. If anything, the new drug was worse than placebo, in that patients improved slower.
In terms of side effects it caused dry mouth, insomnia, and nausea serious enough to make many people quit the study early. But even worse, it raised heart rate by almost 10 beats per minute on average, which is really never a good sign.
So, overall, it was an utter flop. In one sense this is not surprising. New "antidepressants" that don't work in trials have been all too common recently. Just last week we learned about the failure of "Serdaxin" in a Phase II trial. Actually Serdaxin isn't a new drug but an old antibiotic called clavulanic acid that a company was trying to rebrand as a mood lifter.
However the failure of GSK372475 is a bit of a mystery. The drug is a potent triple reuptake inhibitor (TRI) which acts on the neurotransmitters serotonin, noradrenaline and dopamine. By contrast, venlafaxine is a double reuptake inhibitor which doesn't hit dopamine, and paroxetine only targets serotonin. I've written about other TRIs before.
Now it seems surprising that venlafaxine worked, but a TRI didn't, in the same trial. That would imply that blocking the reuptake of dopamine makes you more depressed, enough to cancel out the other actions which are shared with venlafaxine. Which is not what I'd have predicted.
There are other differences between the drugs though. Venlafaxine has a very short half-life - it's broken down in the body in a matter of hours. But GSK372475 has a halflife of 8-10 days. Could this be the problem?
Learned S, Graff O, Roychowdhury S, Moate R, Krishnan KR, Archer G, Modell JG, Alexander R, Zamuner S, Evoniuk G, & Ratti E (2011). Efficacy, safety, and tolerability of a triple reuptake inhibitor GSK372475 in the treatment of patients with major depressive disorder: two randomized, placebo- and active-controlled clinical trials. Journal of psychopharmacology (Oxford, England) PMID: 22048884
Wednesday, November 9, 2011
The authors write that "The present data do not support the notion that brains of male-to-female transexuals are feminized" and conclude "The present study does not support the dogma that male-to-female transexuals have atypical sex dimorphism in the brain".
sentence has gained quite a bit of coverage, including a quote on the Wikipedia page for "transgender".
But is it so simple?
Structural MRI scans were used to compare the size of various brain structures between three groups of volunteers: heterosexual men, heterosexual women and the transexuals (or "MtF"s as I will call them for short) who were diagnosed with gender dysphoria and were "genetically and phenotypically males".
There were 24 in each group, which makes it a decent sized study. None of the MtFs had started hormone treatment yet, so that wasn't a factor, and none of the women were on hormonal contraception.
The scans showed that the non-transsexual male and female brains differed in various ways. Male brains were larger overall but women had increases in the relative volumes of various areas. Male brains were also more asymmetrical.
The key finding was that on average, the MtF brains were not like the female ones. There were some significant differences from the male brains, but they weren't the same differences that distinguished the females from the males.
This is a fairly crude approach. It looks at the groups on average. It's a finding, but there's more you could with this data. It would be better perhaps to look at the male and female groups, and then try to work out which group each individual MtF is most similar to. You could do that using a Support Vector Machine such as was previously used to detect autism.
This would also have the advantage that it would integrate the results across different brain areas: maybe the important thing is not just the size of individual areas but the relative size of one area to another area.
My real problem though is with the language used to discuss the data. The authors say that the study doesn't support "atypical sex dimorphism in the brain" yet this wasn't a study of "the brain". It was a study of one specific aspect of the brain, namely the volume of different regions. There could be all kinds of chemical and microstructural differences that don't show up on these scans.
There are lots of people with severe epilepsy, for example, whose brains clearly differ in some major way from people without epilepsy, yet they look completely normal on MRI. Only using other methods, like EEG, reveals the difference. Because the difference is chemical, not structural.
I have no idea how, or if, the brains of MtF transsexuals are "feminized" but this study doesn't rule it out. Now I'm sure the authors know all this. And in fact they themselves recently published a paper showing atypical neural responses to smelling "oderous steroids" in transsexual people. But while neuroscientists will know what they meant, I worry that studies like this could be miscontrued by other people (like Wikipedia readers) as a result of overenthusiastic language in papers.
Link: Also blogged at BPS Research Digest.
Savic I, & Arver S (2011). Sex dimorphism of the brain in male-to-female transsexuals. Cerebral cortex (New York, N.Y. : 1991), 21 (11), 2525-33 PMID: 21467211
Sunday, November 6, 2011
Abusing drugs and/or alcohol has its side effects, which are not much to be desired, physically, emotionally and/or mentally. Although, with respects to oral health, drug and alcohol abuse can take quite the toll. The affects of addiction can not only cause visual deterioration of the mouth and its workings, but may also cause further illness and/or diseases within the body.
Research was conducted on a group of individuals that were drug and/or alcohol addicts. Some of the drugs that the individuals were addicted to, included that of cocaine, marijuana, meth and opium. When comparing their oral health to that of their lives prior to their addiction, the results were devastating. Most all participants had lost teeth, or were on the verge of severe infections. While others were suffering from heart issues, directly relating to the poor condition of the health of their mouth.
Of all individuals tested, those that were addicted to meth suffered the worst deterioration of all. The ingredients in manufactured meth may include but are not limited to acids, lithium, ether and lye. All of which can be detrimental to the oral, and overall health of a meth user. Some of the common oral health issues that arise with the abuse of meth may include but are not limited to:
When blood vessels break down or are blocked by using meth, the teeth and gums lack the blood that they need to clean themselves efficiently. This can result in tooth decay, teeth falling out, rotting gums and/or heart illness.
Drying of the Mouth:
When abusing meth and/or alcohol, less saliva is produced within the mouth. Blockages of the salivary glands are also commonly evident. As saliva is a natural neutralizer for acidic foods such as soda, citrus and plaque - when there is less of it, the mouth suffers. Teeth begin to break down, and form cavities. It is also often the case, that if not treated, or if the abuse of meth or alcohol does not cease, an individual may lose their teeth over time.
Cracked or Worn Teeth:
It has been reported that over eighty percent of meth users will continually grind their teeth, in and out of sleep. With this consistent clenching and grinding, the teeth begin to wear down. Some meth abusers have even experienced cracks in their teeth from this behavior.
Although the affects that drugs and/or alcohol have on the mouth are often seen, many are unclear as to what the direct causes are.
Continuing her campaign warning of the dangers of modern technology in terms of their effects on the vulnerable brains of the young, the British neuroscientist and Baroness has written another article. This is the latest of many. None of them have been in peer reviewed academic journals.
This one's behind the Great Times Paywall so I can't link to it, but it's called Are video games taking away our identities?
The first part of the article is hard to argue against. Either you'll agree with it or you won't. Personally, videogames as Greenfield describes them bear little resemblance to any games that I've played recently. Similarly for her account of the Internet. But maybe this rings true for some:
Greenfield then moves into discussing the brain, and this is where the science comes in. This is her "home turf" - she's Professor of physiology at Oxford. Yet it's a shambles.
There is one alarm bell ringing, which suggests that increasing 2D screen existence may be having undesirable effects: it is the threefold increase over the past decade in prescriptions for drugs for attention deficit hyperactivity disorder.
While this could be due to changes in doctors’ prescribing procedures, or indeed to a greater recognition and medicalisation of attentional problems, a third possibility could indeed be that if the young brain is exposed from the outset to a world of fast action-reaction, of instant new screen images flashing up with each press of a key, then such rapid interchange might lead to a shorter attention span.
The human condition can be basically divided into two alternating modes, first described by Euripedes... the rational “bread force”, characterised by a strong cognitive take on the world — a personalised past, present and future, in turn related to an active prefrontal cortex and lower levels of the brain chemical dopamine; and the “wine force”, more the state of young children or those adults indulging in “letting themselves go”, in situations perhaps involving wine, women and song, where a strong sensory environment demands less reflection, more passive reaction.
...An increase in physiological arousal can be linked to excessive release of dopamine. Could the screen experience be tilting this ancient balance in favour of the more infantile, senses-driven brain state?Greenfield says that high dopamine and low prefrontal cortex activity is associated with irrationality and a deficit in attention. Video games are causing a flood of dopamine and causing ADHD. That would make sense, if ADHD was caused by too much dopamine, and if drugs for ADHD reduced dopamine release.
The problem is that it's the exact opposite. Drugs for ADHD increase dopamine release and ADHD is widely believed (although it's controversial) to be caused by a dopamine deficit.
Greenfield then says "We know too that dopamine suppresses the activity of neurons in the prefrontal cortex", but this is a serious oversimplification. Dopamine has complex effects on target neurons. It can inhibit firing, but it can also excite it. It all depends on the conditions. Here's what the authors of an influential scientific review said in 2004: "It is agreed by most researchers is that dopamine is a neuromodulator and is clearly not an excitatory or inhibitory neurotransmitter"
Some say that dopamine helps to "tune" the prefrontal by increasing the signal to noise ratio - more signal, less noise. Here's one of the most cited papers about dopamine and the PFC: Cognitive deficit caused by regional depletion of dopamine in prefrontal cortex of rhesus monkey.
Remember that drugs for ADHD like Ritalin, which are sometimes used illicitly by students without that disorder to help them focus and concentrate, cause dopamine release. If Greenfield were right, it would be the exact opposite.
...[other] people characterised by an underactive prefrontal cortex are those with schizophrenia, this time not due to physical damage but rather a chemical imbalance, in particular an excessive amount of the transmitter dopamine. In schizophrenia, like children, the patient is easily distracted, cannot interpret proverbs, is not strong on metaphor but takes the world literally; it is a vibrant world that can implode on, and overwhelm, the fragile firewall of the schizophrenic mindset.This again is a serious simplification. Actually, you don't need to be a neuroscientist to work that out. Just recall the earlier bit: Greenfield has said that ADHD is caused by too much dopamine leading to an underactive prefrontal cortex. Now she says that schizophrenia is the same. So why are the symptoms of ADHD completely different from schizophrenia?
Why is it, in fact, that Ritalin and similar dopamine releasing drugs help with ADHD, but can make schizophrenia worse?
As a neuroscientist, I can tell you that we don't really know what's going on with dopamine in ADHD or schizophrenia. There's decent evidence that dopamine is involved in schizophrenia, but not in any straightforward sense. Schizophrenia is now believed to be linked to reduced dopamine in the prefrontal cortex, and too much in other areas.
As for ADHD, remember: the leading theory is that it's about too little dopamine. Not too much.
The only disease that we know certainly is associated with too little dopamine is Parkinson's. Contrary to Greenfield's theory, people with Parkinson's often have cognitive and mood problems as well as the better known difficulties with movements. They're not super intelligent, prefrontal-cortex-wielding geniuses.
I appreciate that an opinion piece in the Times is never going to be a rigorously argued scientific paper, but the fact that Greenfield's article contains several claims which are the exact opposite of the truth (or at least of current scientific thinking) calls her credibility into serious question.